The invention relates to a method for the operation of wind power plants, more specifically to a method for the operation of a wind power plant with controllable effective power, wherein an idle power interval is assigned to each effective power and the delivered idle power within this idle power interval is controllable
In the case of the operation of wind power plants, it is known to also create idle power in addition to the effective power that is important for energy generation. The idle power can on one hand serve to compensate an idle resistance generated by individual components of the wind power plant in order not to load a mains power supply coupled with the wind power plant. Additionally, a support of the voltage of the mains power supply can also be achieved through a targeted allocation of idle power, Normally, the idle power is determined by the specification of a so-called power factor cos φ, which can cover a certain value range, e.g. from 0.95 capacitive to 0.95 inductive. The phase angle φ thereby describes the phase displacement between voltage and power. The power factor cos φ then corresponds with the ratio between the effective power P and the apparent power S:cos φ=P/S.
The following correlation applies for the apparent power S:S2=P2+Q2.
For a specified power factor, the idle power is proportional to the effective power so that, in the case of a low effective power, only a low idle power is generally made available. If the power factor is specified, for example by the operator of the mains power supply, the maximum possible idle power cannot be created in partial load mode.
At the same time, the electrical components of the wind power plant must be designed such that the current flow set for the maximum effective and idle power does not lead to an overload. As a general rule, the electrical components are to be designed such that they even withstand the load in the case of an effective power lying above the nominal power for a short period of time and—simultaneously—maximum idle power.
In the case of the known wind power plants, the created effective power generally results from the wind conditions. In order to protect the wind power plant from an overload at high wind speeds, the effective power is restricted to a maximum value. This generally results in a speed regulation of the rotor or generator by varying the adjustment angle of the rotor blades for the predetermined, maximum torque, wherein the effective power is regulated to the desired maximum value.
DE 100 59 018 A1, the entire contents of which is incorporated herein by reference, specifies a method for the operation of a wind power plant, in which the regulation of the idle power takes place depending on the effective power mainly determined by the wind conditions such that a constant apparent power is set. The apparent power of the wind power plant is thus independent on the amount of wind. In the known method, it is also provided to deviate from the constant apparent power if the released effective power or idle power should not exceed a specified maximum value.
EP 1 508 951 A1, the entire contents of which is incorporated herein by reference, specifies a method for the operation of a wind farm with a plurality of wind power plants that are linked together and feed effective and idle power to a mains power supply via a hub point. A primary control thereby specifies set-target values for the effective and idle power of individual wind power plants. The goal is to support the voltage on the hub point in that a certain idle power is made available to the entire wind farm and at the same time to minimize the load of the network connecting these plants through an optimized distribution of effective and idle power to be created to the individual wind power plants. The idle power provided by one single wind power plant can thereby lie for a certain effective power value within a range depending on the permissible amperage in the rotor and stator coils of the generator. In particular, it is thereby possible to also provide a high idle power in the case of low effective powers.
DE 103 44 392 A1, the entire contents of which is incorporated herein by reference, specifies a wind power plant with an idle power control module and a device for determining a minimum safe effective power. Based on a supporting idle current desired for the support of the network in the case of voltage decreases, the idle power control module controls the idle power fed into the network. On one hand, this ensures that the supplied effective power does not drop below a minimum value specified by the device for determining a minimum safe effective power; on the other hand, a fixed, specified, maximum apparent power is taken into consideration. The target values for effective and idle power are corrected in a multi-stage method of calculation.
Based on this, the object of the invention is to provide a method for the operation of a wind energy power plant in which a specified idle power can be achieved regardless of the wind conditions.